Help with front caliper

[rcuttler]

Just purchased a 1977 CB750k. It's in pretty good condition other than the fact it has been sitting man years. I've got it running pretty well but the front brake was not functional. Rather than chase the problem down part by part i replaced everything from the master to the hoses to the caliper. The original caliper was severely corroded. The caliper mounting bracket has some type of spring loaded alignment device that I didn't have on my 1971 K1 from 46 years ago. My Clymer manual makes no mention of this device. How do I adjust\align the caliper? TIA

R Cuttler

[amc49]

The service manual shows even the first year ones to have some version of the mechanism there, it adjusts the caliper freeplay. Bike on centerstand and weight on back to hold front wheel off ground. The caliper moving piston likely needs to be backed off a little to allow for freeplay to exist. Loosen the locknut on the long bolt and turn the bolt while spinning wheel by hand, it will either stay loose or start to tighten up depending on which way you turn the long bolt. You are swinging the caliper sideways to make the non-movable side with no piston drag the disc or get further away from it. When you figure out which way tightens the wheel to drag then back off and barely adjust it again to just begin to drag the wheel and then back off 1/4 turn from that to loosen the wheel to free spinning and then tighten the locknut. Be sure to then grab brake handle and pump the brake up a couple times to then move the caliper in tight to work right.

The adjustment takes all excess freeplay out of the caliper so that the brake works pretty much instantly, you have to end up with just enough play left to allow the wheel to turn free of course. As both pads wear later in life you may have to adjust one more time or so. With new pads you start all over since the non-moving side pad changed thickness by a whopping amount.

Long bolt too far one way and the wheel drags to try to lock up. The other way you grab for brake but nothing seems to happen as you are simply applying the piston to make the caliper swing sideways in the excess play, there is nothing to stop it because that bolt is loose. At some point the caliper WILL swing to finally run out of play and then brake works but you adjust the arrangement to already be right there where you need it to brake instantly while still enough play for wheel to turn freely. Correct also makes sure the piston is not sticking too far out of the caliper, with it too loose you would have been pumping the piston further and further out and too far.

IIRC turning the screwdriver slot in long bolt clockwise tightens the wheel up to drag.

[rcuttler]

Mr. Guru you definitely have earned that name today. Thank you very much.

Bob